Reductive alkylation of azoarenes to <i>N</i>-alkylated hydrazines enabled by hexafluoroisopropanol

A one-pot tandem approach to <i>N</i>-alkyl-<i>N</i>,<i>N</i>'-diarylhydrazines was developed using a sequence of reduction of azoarene to hydrazoarene followed by reductive alkylation by an aldehyde. The mild reaction conditions suppress <i>N</i>-<i>N</i> cleaved products and selectively provide trisubstituted hydrazine derivatives. The mechanistic study demonstrates that the iminium formation step is likely to be the rate-limiting step.